An elastomeric bushing is a structural element which is primarily although not exclusively used in vehicle suspension systems. The primary task of elastomeric suspension bushings is to provide isolation of the vehicle body from undesired vibration and shocks without affecting the steering, ride, and handling characteristics of the vehicle during its useful life. The elastomeric bushing kinematically links two suspension members while dampening the loads they transmit from the wheel to the body or the frame of the vehicle. Vehicle suspension bushings typically consist of an annular cylinder of an elastomeric material (e.g., natural rubber, synthetic rubber or polyurethane) inside a metallic casting or outer tube. Often they also include an internal crush tube which protects the bushing from being crushed by the bushing clamping features.
In recent years, due to global warming concerns, regulation of the vehicle emissions of CO2 has become more stringent. This has driven a high demand for vehicle weight reduction but without any compromise in the customer ride quality and comfort which has presented a challenge when designing suspension bushings using conventional elastomeric materials that have inherent physical limitations.
For elastomeric materials, the relationship between the force or moment applied to the outer or inner sleeve or the tube of the bushing and the relative displacements or rotations is nonlinear, namely, the one that has pronounced elastic hysteresis. Correspondingly, elastomeric bushings transfer the deformation strain energy into heat during their loading and unloading, thus providing damping to the joint. Excessive heat tends to harden the elastomeric material. As the bushing material hardens, it tends to crack, break, and then disintegrate. Its temperature determines the life of a bushing. Rough road conditions and/or defective shock absorbers or struts will allow excessive suspension movement creating more heat, which shortens the life of the bushings. Elastomeric materials commonly used in vehicle suspension bushings have relatively low thermal conductivity which does not allow for a quick transmission of the heat away from elastomeric material to the inner or outer bushing sleeves. To address such a challenge, hydraulically damping suspension bushings that utilize the principle of the hydraulic damping have been developed as illustrated, for example, in U.S. Pub. No. 2007/0045918 A1. However, these types of bushings are relatively expensive and, as a result, are not widely used in production. Therefore, an increase in the overall thermal conductivity of suspension bushings is highly desired for more effective heat dissipation into environment in order to prevent the undesirable noise and vibration levels or even a total bushing failure due to the material fatigue.
As in so many areas of manufacturing technology, there is always room for improvement related to undesirable noise and vibration associated with metallic materials conventionally used in a wide array of mechanical and structural components.